A vehicle-to-vehicle communication system including a plurality of vehicle-mounted communication apparatus, each of which is mounted on a vehicle, wherein the plurality of vehicle-mounted communication apparatus transmit and receive packet information to and from each other, is widely known. The vehicle-mounted communication apparatus transmits packet information including information relating to the vehicle mounted therewith, causing an address assigned to the relevant vehicle-mounted communication apparatus to be included as a transmission source address. Another vehicle-mounted communication apparatus which has received the packet information, based on the transmission source address included therein, identifies the vehicle-mounted communication apparatus which has transmitted the packet information, and acquires the information relating to the vehicle mounted with the identified vehicle-mounted communication apparatus. The other vehicle-mounted communication apparatus, in the event of transmitting another item of packet information with the vehicle-mounted communication apparatus which has transmitted the packet information as a destination, transmits packet information in which the transmission source address included in the received packet information is caused to be included as a destination address.
Patent Document 1: JP-A-2006-325019